More amps from DC 13.7v (full charge)

[RAVEN]

Hey guys I am at a bit of a loss. I want to build a light weight eSBK. From what I have seen most of these machine weigh in excess of 500lbs. That is entering Sport Tourer territory. And even with 100ft-lb's of torque; that's still an under performing bike. The motor I have chosen is an Agni M95 Re-inforced 5000 rpm model . It taks 72 volts to get that high and has a 400aH draw at full draw. The batteries I have chosen are 4 Braille B128L LiOn batteries and at full charge they are rated at 13.7 volts. So, theoretically I will have 54+ volts on tap. I know that I can use a step-up tranformer to get the rest or possibly the whole 72 volts from each battery individulay? Now how do I increase the amps? I figure If I can do that; I can effectively increase the life of my batteries. You know kind of like increasing mpg on a car using the same power but less fuel consumption.

So, any advise or help?

- Isaac

 

[amberwolf]

It's not that simple. You can get more voltage using a DC-DC converter (what you call a tranformer), but it will *reduce* the amount of current you can draw, since more current is already needed in order to power the DC-DC converter itself to maintain the same total power output at the higher voltage.

If it needs 400 battery amps to run the motor/controller configuration you are after, you will need to start with a battery pack that can supply that much current for the duration that you need to draw that much current. If you don't, you'll need to start with a battery pack that starts at a much higher voltage so that you can still draw the same power out of it and get that current and the voltage you need.

Doing it that way will lose a whole lot of power in the conversion process.

If you're not doing a conversion and you have a battery pack that can supply your max current needs, it'll also need to start at or above the max voltage you will need it at.

You can always cut voltage down, in the controller, by not using full throttle. But increasing the voltage requires a differently-designed controller that can do boost as well as buck, so you'd need to make sure the controller you get can do that, and still work with the motor you will use.

You can't get more power out of the pack than it is able to supply; you can convert it from one form to another and one level to another but always at the cost of lost and wasted power (and excess heat), which means loss of range in the long run.